1. The Field of the Invention
The invention generally relates to the field of interventional procedures. More specifically, the invention relates to interventional procedures that require the placing of a stent in a body lumen, such as a body lumen of a patient or animal.
2. The Relevant Technology
Human blood vessels often become occluded or blocked by plaque, thrombi, other deposits, or material that reduce the blood carrying capacity of the vessel. Should the blockage occur at a critical place in the circulatory system, serious and permanent injury, and even death, can occur. To prevent this, some form of medical intervention is usually performed when significant occlusion is detected.
Several procedures are now used to open these stenosed or occluded: blood vessels in a patient caused by the deposit of plaque or other material on the walls of the blood vessel. Angioplasty, for example, is a widely known procedure wherein an inflatable balloon is introduced into the occluded region. The balloon is inflated, dilating the occlusion, and thereby increasing the intra-luminal diameter.
Another procedure is atherectomy. During atherectomy, a catheter is inserted into a narrowed artery to remove the matter occluding or narrowing the artery, i.e., fatty material. The catheter includes a rotating blade or cutter disposed in the top thereof. When the blade is rotated, portions of the fatty material are shaved off and retained with the interior lumen of the catheter. This process is repeated until a sufficient amount of fatty material is removed and substantially normal blood flow is resumed.
In another procedure, introducing a stent into the stenosed region to open the lumen of the vessel treats stenosis within the artery or other blood vessel. The stent typically includes a substantially cylindrical tube or mesh sleeve made from such material as stainless steel or nitinol. The design of the material permits the diameter of the stent to be radially expanded, while still providing sufficient rigidity such that the stent maintains its shape once it has been enlarged to a desired size.
To place a stent, many medical devices are typically used in combination. Typically, a small diameter guidewire is inserted through the arterial system, by way of the femoral artery, and guided to the point distal to the stenosed region.
Once the guidewire is placed, the guidewire is used as a guide for all of the other devices that are used in the procedure. These devices have an inner lumen through which the proximal end of the guidewire, which is outside of the body of the patient, is inserted. The device is then slid along the guidewire into the body, allowing the guidewire to guide the device to the required position in the vascular system. Sliding another device over the guidewire is commonly known as an exchange.
Two basic types of devices facilitate exchanging of other medical devices. The first type of device encloses a guidewire within an inner lumen of the device for the entire length of the device. The second type of device only encloses the guidewire for a small distal segment of the device, with the remainder of the guidewire exiting from the inner lumen of the device through a side hole to allow the device and the guidewire to be side by side. In both cases, control of the guidewire is paramount during the exchange as the correct positioning of the device is reliant upon maintaining the position of the guidewire; this being difficult as at least a section of the guidewire is inaccessible due to it being enclosed in the inner lumen of the device being exchanged.
Following access by the guidewire, a guide catheter is typically inserted into the artery and about the guidewire so that the tip thereof can be guided to a position just proximal to the stenosed region to be treated. This guide catheter serves the purpose of allowing other devices to rapidly be delivered to that position without each being carefully guided over the guidewire from the point of access, through the tortuous anatomy of the arterial system, to the point of intervention.
When guidewire access to the lesion is established, and if there is sufficient cross sectional area in the narrowed part of the lesion, a stent, mounted on a delivery device, is delivered over the guidewire and through the guide catheter. When correctly placed within the stenosed region, the stent will then be deployed, propping open the vessel at that point.
Various types of stents are used in these cases, but a common one requires that the stent be deployed, or expanded from a compressed state by a balloon upon which it is mounted. The balloon is inflated from the proximal end of the delivery device to a high pressure, which both opens the stenosis and embeds the stent into the inner lumen of the vessel at that point. Generally, the typical method to deliver and deploy a stent is complex, with multiple changes in the medical device slide over the guidewire and fluids to inflate the balloon deploying the stent.
Providing a stent delivery device that reduces the complexity of an interventional procedure would advance the art of stent delivery. Furthermore, reducing the number of devices used to perform a stent implanting procedure would advance the art of stent delivery.